1. Field of the Invention
The present invention relates to a motor and a recording disk driving device having the same, and more particularly, to a motor in which vibration characteristics are improved by increasing the strength of a fluid dynamic pressure bearing, and a recording disk driving device having the same.
2. Description of the Related Art
A hard disk drive (HDD), one of various information storage devices, reads data stored in a disk or writes data to the disk using a read/write head.
The hard disk drive requires a disk driving device capable of driving the disk. As the disk driving device, a small-sized motor is used.
In the small-sized motor, a fluid dynamic pressure bearing assembly has been used. A shaft, a rotating member of the fluid dynamic pressure bearing assembly, and a sleeve, a fixed member thereof include oil interposed therebetween, such that the shaft is supported by fluid pressure generated by the oil.
That is, in the motor, the oil is provided in a micro clearance between the sleeve and the shaft, and the fluid pressure supporting the shaft is generated by a dynamic pressure groove formed in the sleeve or the shaft.
Here, the center of gravity of the motor is generally positioned at an upper portion thereof, and fluid pressure from a dynamic pressure groove positioned at the upper portion of the motor is an important factor in determining the rotational characteristics of the motor.
However, in the case of the motor according to the related art, the fluid dynamic pressure supporting a shaft is the same at an upper portion and a lower portion of the shaft, such that a problem is generated in view of stable rotational characteristics. Therefore, vibrations are generated at the time of rotation of a rotating member, such that the performance of the motor may be inefficient.
In addition, when the rotating member of the motor rotates, a majority of the overall friction is caused by friction in a position in which the dynamic pressure groove is formed and power consumption for driving the motor is inevitably increased due to the friction.
In addition, when the amount of oil is reduced as compared to a normal level of oil due to various causes such as oil evaporation, oil leakage, and the like, the introduction of air bubbles from the outside and the friction between the rotating member and the fixed member further increase, such that it is difficult to secure floating force for rotation, thereby deteriorating the rotational characteristics of the rotating member.
Therefore, in the motor, research into technology for reducing friction, minimizing power consumption in the driving of the motor, securing a storage space for the oil, and implementing stable rotational characteristics has been urgently demanded.